1. Field of the Invention
The present invention relates: generally to land vehicles; more specifically to electric land vehicles; and most particularly to electric land vehicles with reversible field motors enabling regenerative braking whereby the kinetic energy of the moving vehicle is converted to electricity.
2. General Background
Reversible field motors have two polarities: motor and generator: respectively powered by electricity in drive or motor polarity, and generating electricity in braking or generator polarity, between the two opposed rotating electromagnetic fields (EMFs) required. The second rotating EMF is usually a product of alternating current induced by the first rotating EMF which is produced by alternating current (AC) supplied to the primary windings, usually in the stator. An EMF is produced by AC and a rotating EMF will induce AC in appropriately positioned, while rotating, secondary or field windings. For these fundamental factors reversible field motors capable of providing regenerative braking generally require alternating current.
But for a land vehicle to be able to store the energy converted, the AC generated by the reversible field motor in generator polarity must be converted to direct current (DC) for storage in batteries. The internal combustion engine (ICE) in a conventional automobile, moreover, is started with an AC electric motor that, with an alternator, routinely generates AC and converts it to DC to replenish the conventional 12 volt lead acid battery that is fully recyclable as mandated by Federal and State law and regulations and will easily last for decades if properly maintained: if the plates are simply kept submerged in electrolyte solution by adding distilled water as indicated.
Reversing the fields of an otherwise conventional electric starter motor enables regeneration of AC by this motor/generator in generating: i.e. braking; polarity, and converting AC into DC is routinely done in conjunction with an alternator for battery storage. Rather than taking shaft power of the ICE to run an alternator with a belt or chain, as historically done on conventional mass produced automobiles, the alternator of an integrated AC Motor Generator Alternator (ACMGA) is aligned with and coupled adjacent to a conventional transmission, between that transmission and the drive shaft of the ICE on more recent hybrid automobiles. But at this point one verges on the most pertinent known prior, contemporary, and even prospective art discussed directly below.
3. Discussion of the Pertinent Prior Art
In modern, i.e. computer or information age, reverse chronological order one begins with the yet to be manufactured Chevy Volt, announced in the summer of 2007, and proceeds to the Tesla, expected out this year: 2009. As advertised in 2007:                The Volt, with its revolutionary GM® E-Flex Propulsion System, is different than any previous electric vehicle because it will use a High-Energy Battery and range-extending onboard source that can run on gas, ethanol, or biodiesel to recharge the battery while driving. For someone who drives less than 40 miles a day, Chevy Volt will use zero gasoline and produce zero emissions. (emphasis added, ‘Gas-friendly to gas-free.’ Chevy ©2007 GM Corp., magazine advertising ‘booklet’ with 16 faces, 5 in.2).The Volt is expected to be a plug-in hybrid, with batteries rechargeable through an AC/DC converter yielding a range of forty miles and using an ICE to extend range. The “High-Energy Battery” will comprise Lithium-ion (Li-ion) batteries manufactured by LG of South Korea. And the drive will comprise split shaft transaxles with constant velocity joints to enable drive while steering: i.e. a conventional front end drive train; including conventional transmission.        
The Tesla, expected later this year: 2009; will use a powerful DC reversible field motor (DCRFM), a new technology discussed in detail further below, coupled to a conventional rear wheel drive configuration with Borg-Warner transmission restricted to a single gear ratio of about 1:8.3 and a mega-cell, non-recyclable, assemblage of laptop type Li-ion batteries, with safety admittedly the largest design concern, requiring replacement within five years maximum and costing at least $30,000.
In consideration of less new, actually already on the road technology, the Honda Insight and the Toyota Prius are considered both true, as well as being non-plug-in, hybrid vehicles in utilizing an integrated ACMGA providing regenerative braking and electric drive though primarily using an ICE through the ACMGA in conventional, non-electric, drive. The prospective Volt is understood at present to favor an auxiliary enginator: an ICE coupled to an electric generator powering an ACMGA coupled to the conventional front wheel drive train; and might be considered fully electrically driven as opposed to a hybrid, if it actually existed today.
The ACMGA developed and used by Honda is widely recognized as the best known technology available today. Of a ‘pancake’ design Honda achieves over twenty percent (20%) greater efficiency over all previous reversible field motors by staggering the field poles, increasing modestly the thickness, but packing into the same diameter over twenty-five percent (25%) more EMF strength. Over twenty percent more power, in other words, is obtained by a geometrically efficient design. Geometry is important to electricity as current is carried on the surface of conductors and rotating opposed EMFs are required of reversible field motors required to provide regenerative braking which until very recently had been thought to require an AC motor.
In brief, Tesla is the only known exception to the pertinent prior art otherwise characterized by use of one reversible field AC motor/generator combined with an alternator to convert DC to AC and AC to DC. All the pertinent prior art, including Tesla, is characterized by powering the driven wheels with a single electric motor, with or without auxiliary ICE or enginator, coupled to a conventional central transmission splitting drive to the two driven wheels, front or rear. Tesla hence must be considered the most pertinent art known for use of a DC Reversible Field Motor (DCRFM) powered directly by a DC power source. The other pertinent art including the prospective Volt, despite intended plug-in capability, only achieves regenerative braking with an ACMGA and all the known pertinent art, prior and otherwise, utilizes or intends to utilize a conventional drive train including a conventional transmission whereby shaft power is transferred from a single source of shaft power through an entire drive train intended: i.e. designed and manufactured; for ICE drive.
The Tesla obviates the need for an ACMGA but at a price: its DC motor cannot drive a conventional transmission with multiple gearing ratios. The Tesla is ‘drive by wire’ but this in no way prohibits change of gearing on the otherwise conventional Borg Warner transmission restricted to a single gear ratio. The impediment is the electric motor which inherently has huge torque compared with an ICE: the Tesla needs the lowest gear ratio available on the strongest conventional transmission available because the electric motor has more than several times the torque of an ICE of equivalent horsepower. Use of low gearing exclusively is the most inefficient for the transmission and the drive train generally but the only ‘off the shelf’ option available to the Tesla because of the huge amount of torque inherent to an electric motor, particularly DC.
Overcoming inertia is considered the largest impediment to a fully electric land vehicle. A clutch makes physical contact to enable an ICE to move a vehicle from rest while an electric motor has only the opposed EMFs between stator and rotor windings. At initial start up any electric motor, in theory, has infinite voltage and no current. This practically impossible condition has historically been ameliorated by physically rotating the rotor, with armature windings, on an AC motor before energizing: cranking a vintage car by hand, kick starting a scooter engine, pull starting a mower or outboard ICE; while shunts were used on DC motors to overcome the infinite voltage zero current conundrum existing at start which is likened to the condition of a vehicle at rest: a condition of infinite mass relative to actual velocity.
Statement of Need
Electric drive of a full size land vehicle is considered in broad terms to demand a choice between huge electric power and battery pack to match as in the Tesla plus reliance upon the lowest gear available on a conventional transmission or reliance upon a conventional ICE as in the Toyota Prius or Honda Insight. The inherent characteristics of an electric motor are recognized as comprising a fundamental impediment to overcoming the inertia of a full sized land vehicle at rest just as an electric motor, by theory, has infinite voltage and zero current at start. Electromagnetic torque, essentially, is opposed to mechanical inertia.
A need is hence discerned for an economic avenue around or through this impediment: an electric automobile cannot sell for $30,000 if its battery pack costs $20,000; and this need further suggests a need for greater efficiency in transmission of shaft power in electric drive of a land vehicle: i.e. reduction in drive train friction and inertia; than that obtainable using a conventional central transmission intended for relatively low torque ICE shaft power.